The prevalence of depression among adults in the U.S. stands at 9%, according to a CDC analysis of survey data.

The prevalence of depression among adults in the U.S. stands at 9%, according to a CDC analysis of survey data.

This includes 3.4% who have major depression, the agency reported in the Oct. 1 issue of Morbidity and Mortality Weekly Report.

Agency analysts looked at data from the Behavioral Risk Factor Surveillance System (BRFSS) surveys conducted in 2006 and 2008 among 235,067 adults in 45 states, the District of Columbia, Puerto Rico, and the U.S. Virgin Islands.

Depression was assessed in telephone interviews using the Patient Health Questionnaire-8, which includes eight of the nine criteria for depression listed in DSM-IV.

Participants were classified as having major depression if, on more than half of the days during the preceding two weeks, they met five of the eight DSM-IV criteria, plus felt "little interest or pleasure in doing things," or "feeling down, depressed, or hopeless."

Participants were considered to have "other depression" (minor or dysthymic) if they reported at least two criteria plus one of the two specified feelings associated with depression.

The survey data revealed that the prevalence of major depression was highest -- at 4.6% -- among those ages 45 to 64 and lowest (1.6%) among those 65 and older. Prevalence among young adults 18 to 24 was 2.8%.

Women were more likely to report more major depression than men (4% versus 2.7%), and people lacking health insurance were more likely than the insured to report signs of major depression (5.9% versus 2.9%).

Depression -- of any degree -- had its biggest impact when examined by employment status, with 39.1% of those classified as unable to work reporting current depression and 22.2% of them reporting major depression. Among those who were unemployed, 21.3% were currently depressed, and 9.8% reported major depression.

In an editorial note, the agency confirmed that the sociodemographic findings in this survey are similar to those in other studies looking at the prevalence of depression within the previous 12 months.

The editors observed that the reasons why women report more depression are not entirely clear, but may relate to hormonal differences and genetic factors.

They also noted that the finding of higher rates of depression among minorities may reflect risk factors for mental illness including less access to care, chronic disease, and social and economic inequality.

"Targeted efforts are needed to address racial/ethnic disparities in recognition and treatment of depression," the CDC editors stated.

Similarly, they noted, regional differences in depression may result from higher rates of comorbid physical and mental conditions and decreased availability of mental health services.

The seven states with the highest rates of depression were in the South -- Alabama, Arkansas, Louisiana, Mississippi, Oklahoma, Tennessee, and West Virginia. All had rates of depression from 10.4% to 14.8%. Puerto Rico had the second highest depression rate in the survey at 14.7%.

"The variations among states in depression prevalence should be examined further to target prevention and intervention efforts and to allocate mental health treatment resources of the federal government," the editors wrote.

Limitations of the report included the decrease in BRFSS survey responses because more households have only cell phones, and the omission of the homeless and institutionalized.

State public health departments should continue to conduct surveillance on depression, targeting populations at risk and in need of intervention, CDC recommended.

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